Transcript of "Acids and bases dr.surendran prambadath"

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Acids and Bases are two classes of chemicalcompounds that display generally oppositecharacteristics.When aqueous solution of an acid and a base arecombines, a neutralization reaction occurs.This reaction is very rapid and generally produceswater and a salt. HCl + NaOH NaCl + H2O

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Arrhenius Concept of Acids & Basesa) An acid is a substance which gives hydrogen ions, H+ when dissolved in water.b) A base is a substance which gives hydroxyl ions, OH- when dissolved in water.c) Neutralization is the combination of H+ ions from acid and OH- ions from the base forming H2O.

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Lewis Concept of Acids & Basesa) An acid is an electron pair acceptor.b) A base is an electron pair donor.c) During neutralization, base donates an electron pair to the acid forming a co-ordinate bond.

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During Redox reaction,Oxidation and reduction will take placetogether.An oxidising agent will get reduced andreducing agent will get oxidised.Understand…….oxidising agent……reducing agent……

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Oxidation NumberOxidation number or oxidation state isdefined by the total number of electronsthat an atom either gains or loses in orderto form a chemical bond with anotheratom. Make it by heart……..!

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Rules for assigning oxidation number1 The algebraic sum of the oxidation numbers of all atoms in a compound is zero.2 Oxidation number of an element in its elementary state is zero.3 Oxidation number of all metals in all compounds is positive.4 Oxidation number of all non-metals in all compounds is negative.5 Oxidation number of hydrogen is +1, but in hydrides it is -1. (NaH, MgH 2)6 Oxidation number of oxygen is -2, but in peroxides it is -1 and in OF 2 it is +2.7 Oxidation number of first group element is is +1 and that of second group element it is +2.8 The oxidation number of the elements in their molecules like H 2, N2, Cl2, Br2, O2 etc is zero.9 The oxidation number of a simple ion is equal to the charge on the ion.

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Parts of Daniel cell1.Two half cells, namely zinc half cell and copper half cell. In the former is a zinc rod dipped in a ZnSO4 solution and thelatter is a copper rod dipped in a CuSO4 solution. The twometallic rods are called electrodes.2. The two half cells are connected externally by a metallic wireto a galvanometer through a key and internally by a salt bridge.3. The salt bridge is an inverted U-tube containing an arousesolution of an inert salt like KCl, KNO3, NH4NO3 to which someagar-agar or gelatin has been added to convert it into a semi solid,ie gel. The ends of the U-tube are plugged with glass wool.

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1.Permits the passage of electric current internally,2.Maintains the electrical neutrality of the solution,3.Prevents intermixing of the solutions,4.It does not take part in cell reaction. Representation of Daniel Cell Zn(s) / Zn2+(aq) // Cu2+(aq)/Cu(s)